1. Field of the Invention
This invention is the process of reacting chlorosulfonic acid with a selected ester of a halofluoroacetic acid to produce the corresponding acid chloride.
2. Prior Art
Acid chlorides are generally prepared by reacting an acid with a compound such as PCl.sub.5. Young et al., J.A.C.S. 71, 2432 (2433) (1949), described the preparation of chlorofluoroacetyl chloride in two steps. The corresponding ester is first hydrolyzed to the acid and the acid is then treated with PCl.sub.5 to give the acid chloride.
U.S. Pat. No. 3,742,047 to E. J. Prill discloses, as in Example 8, reacting chlorosulfonic acid with an acid to yield an acid chloride.
M. Schmidt et al., Ber. 98, 1003 (1965) shows the preparation of acyl chlorides by the reaction of an acyl anhydride with chlorosulfonic acid.
British Pat. No. 679,185 (1952) issued to Henkel and Cie shows the reaction of an alkyl benzene sulfonic acid with chlorosulfonic acid to produce an alkyl benzene sulfonic acid chloride.
R. B. Wagner et al., Synthetic Organic Chemistry (1953) pages 547 and 548 show the preparation of ethoxalyl chloride by the reaction of phosphorus pentachloride on ethyl oxalate, or by the reaction of thionyl chloride on potassium ethyl oxalate.
Synthesis of chlorofluoroacetyl chloride from the corresponding acid is not practical on a kilogram scale because of the difficulties in isolating and purifying the highly water soluble and hygroscopic acid. A synthesis based on converting the anhydrous sodium salt of chlorofluoroacetic acid to the acid chloride has also shown difficulties on scale-up. The sodium salt is an extremely hygroscopic, hard, intractable solid that cannot be easily removed from the vessel in which it is deposited by evaporation. Also, it is thermally unstable and subject to decomposition during the drying process.